Maximum transmit power 0 lower than Current power 5

Installing and Using OpenWrt
1 
Maximum transmit power **0** dBm
Current power: **5** dBm

Why this, I have similar configurations with other routers and there the Maximum transmit power 0 dBm is the same as the Current power 0 dBm

Actually I use an Archer C7 as wireless bridge and an ethernet cable instead of an USB-wifi-dongle in a dvb receiver. An access point is configured, but nearly never used, so I like to reduce power to minimize influence on my other routers with a similar task.

I tested it with my phone. 0dB is fine in a distance of 5m.

2

Maybe this is a "feature" of the Archer C7. A 2nd C7 has the same behavior. Set 0dBm, used 5dBm. This means the signal is a lot stronger than needed and influences maybe the other wireless bridges.